Field of the Invention
The present invention relates to current feed-throughs used to provide an electrically conductive path through the wall of a vessel, which path is electrically isolated from the vessel itself.
In particular, the present invention relates to such current feed-throughs which are suitable for providing current to, and removing current from, superconducting structures within a vacuum vessel or a cryogen vessel.
Description of the Prior Art
In the case of modern superconducting magnets for MRI systems, for example, it may be required to provide an electrical current path from a superconducting coil assembly which is contained in one cryogen vessel, and a superconducting switch which may be provided external to the cryogen vessel, or even enclosed within a second cryogen vessel.
While the MRI magnet provides an example of a possible field of use of the present invention, the present invention is not restricted to such field of use, and may be applied in numerous other situations.
Examples of current feed-throughs are described in:
MESSER GRIESHEIM GMBH MESG-S European Patent EP 0 510 397;
Section 6.5 of the MDC Vacuum Ltd catalogue (www.mdcvacuum.co.uk); and
M. Kuchnir “Fabrication of Cryogenic Electrical Feedthroughs” FERMILAB TM-596 Aug. 8, 1975 at http://lss.fnal.gov/archive/tm/TM-0596.pdf.
It is preferred that such feed-throughs should have the minimum possible electrical resistance at the temperature of operation of the superconducting magnet and the superconducting switch. The feed-throughs must be capable of supporting a vacuum on one side, and cryogen pressure on the other.